Forms in 5.7

Well 5.7 is winning me over. However, with so few addons, I'm in need of improving the standard form. I'd like to build a form that has a "quantity" field for numbers. As in, I would like to order 26 widgets. The form would say "Quantity" with a field for the #26. (I'm over explaining probably). Anyway, the trick is, I need it to accept only numbers, AND, most importantly, it must not accept numbers below a certain value. For example, no orders below 25.

I'm open to any suggestions, but I'm certainly not an expert. However, I am willing to read, learn, and try if you all have links to step-by-step material. THANKS!

Another option is making a custom template for the Form block and adding a view.js file that validates the input for your Quantity field. It could prevent submission if the input value is not a number and less than 25.

Both options requiring programming. If that is an issue, maybe someone else might have another option.